After a migration of DHCP from one server to another I found my self trying to unathorize the old server. One way to do it is to select the Server in the DHCP Tool. Then click "Action" on the menu bar and then click "unauthorize." You can accomplish this alos by right-clicking on the server as well and clicking "Unauthorize."
The DHCP server information is retained in active directory. So if you have ever uninstalled DHCP, removed a server, or any other such action without unathoirzing the DHCP server they are still listed in AD. You can read more about why it's listed in AD and so on here.
To see what DHCP servers are currently authorized in DHCP open a command prompt and run the following command "netsh dhcp show server". Upon doing this I noticed a server I had used before that was no longer around. These results will give you two pieces of information you will need to deuathorize the servers from AD. The server name and Address.
Run the following command with your servers information filled in"netsh dhcp delete server [servername] [server ip address]". It should give you a command completed successfully if everything went well. You can re-run the show server command to see if it worked.
I used this command to remove the old server that was no longer used as well as to remove(unauthroize) the server that was giving me the error. Upon doing this I jumped back into the DHCP tool to see if it recognized my change.
Upon right-clicking the server it was showing me the optin to "authorize" the server. This confirmed that netsh worked. I was then able to remove the DHCP role from my server.